CN111092453A - Power grid key line identification method for multipoint access photovoltaic power supply - Google Patents
Power grid key line identification method for multipoint access photovoltaic power supply Download PDFInfo
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Abstract
The invention discloses a power grid key line identification method of a multi-point access photovoltaic power supply, which comprises the steps of obtaining a direct current power flow network model of a power grid; traversing each 'power generation-load' pair in the direct current power flow network model, respectively injecting unit current elements and unit loads into power generation nodes and load nodes of each 'power generation-load' pair, and recording current variation of each line at the moment; judging whether photovoltaic power access exists in power generation nodes and load nodes in each 'power generation-load', updating power weights of the power generation nodes and/or the load nodes according to judgment results, and calculating transmission power weights between the power generation nodes and the load nodes; calculating an improved electrical dielectric value of each line; the improved electrical dielectric values for each line are ordered. The method can identify the key line of the power grid with multipoint access of the photovoltaic power supply, and meets the requirement of the future intelligent power grid safety development.
Description
Technical Field
The invention belongs to the technical field of operation and stability of a new energy grid-connected system, and particularly relates to a method for identifying a power grid key line of a multi-point access photovoltaic power supply.
Background
With the large-scale development of power grids, the topological structure of the power grid is increasingly complex, large-scale power failure events are increased day by day, and the power failure is increased in the early united states to the brazilian blackout in the last year without death. Research shows that the rapid breakdown of the whole regional network caused by the fault of individual elements and lines in the power grid and the subsequent cascading failure is the main cause of major power failure, and few lines with long-range connection often play a role in promoting the wave. With the development of clean energy, the proportion of photovoltaic power sources in a power grid is increased year by year, and the grid connection of a photovoltaic power generation system also has influence on the system. Therefore, when the photovoltaic power supply is connected into the system, the key line of the system can be quickly and accurately identified, and the method has important theoretical basis and practical significance for establishing preventive measures, formulating a power grid operation mode and avoiding damage caused by large-scale power failure accidents.
In recent years, the research shows that domestic and foreign power grids have obvious world characteristics, the characteristic is that key lines of the power grids promote to cause cascading failures to spread rapidly, and the characteristic that the power grids are both robust and fragile can be found by carrying out different types of attacks on power grid elements. The complex network theory is widely applied to power grid vulnerability assessment, and the medium degree of the complex network theory are used for identifying central nodes and key lines. On the basis, students provide electrical betweenness and network efficiency indexes to identify the key line of the power grid while considering the network topology and the electrical characteristics.
In recent years, with the continuous and rapid development of photovoltaic power supplies, the permeability of the photovoltaic power supplies in a power grid is continuously improved, and the development of energy storage technology improves the characteristics of randomness and volatility of the photovoltaic power supplies, but the injection power of a connecting node, the node voltage and the power flow of the power grid can be influenced by the difference of various network access plans of a large number of photovoltaic power supplies. The grid electrical medium index usually depends on the tidal current result, so the electrical medium index of each line will change along with the change of the tidal current.
Disclosure of Invention
Aiming at the problems, the invention provides a power grid key line identification method of a multi-point access photovoltaic power supply, which can identify the power grid key line of the multi-point access photovoltaic power supply, accords with the energy development direction of new energy grid connection at the present stage, and accords with the requirement of the future intelligent power grid safety development.
In order to achieve the technical purpose and achieve the technical effects, the invention is realized by the following technical scheme:
a power grid key line identification method of a multi-point access photovoltaic power supply comprises the following steps:
(1) acquiring a direct current power flow network model of a power grid;
(2) traversing all 'power generation-load' pairs in the direct current power flow network model, injecting unit current elements into power generation nodes in all the 'power generation-load' pairs, injecting unit loads into load nodes, and recording current variation generated by all lines of a power grid when each node pair injects the unit current elements and the unit loads;
(3) traversing all 'power generation-load' pairs in the direct current power flow network model, judging whether photovoltaic power supply access exists in power generation nodes and load nodes in each 'power generation-load', updating power weights of the power generation nodes and/or the load nodes according to a judgment result, and then calculating transmission power weights between the power generation nodes and the load nodes;
(4) calculating an improved electrical dielectric value of each line based on the data obtained in the steps (2) and (3);
(5) and sequencing the improved electric medium values of all the lines to finish the identification of the power grid key lines of the multipoint access photovoltaic power supply.
Optionally, the direct current power flow network model is an undirected weighted graph G ═ V, E, Z, P, B, where a point set V includes a generator, a contact node, and a load node of the power grid; the side set E comprises a transformer branch of a power grid and a power transmission line; the side weight set Z comprises reactance values of the power transmission line; the transmission value set P comprises the maximum transmission power of the transmission line; the adjacency matrix B represents the structural relationship representing the power grid.
Optionally, the direct current power flow network model is obtained based on a complex network theory.
Optionally, if it is determined that a certain power generation node is connected to the photovoltaic power supply, the power weight of the power generation node is calculated according to the following formula:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; sGThe node power injection increment generated by connecting a photovoltaic power supply to a power generation node; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of load node j.
Optionally, if it is determined that a certain load node is connected to the photovoltaic power supply, then:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of the load node j; swThe node power injection increment generated when the photovoltaic power supply is connected to a load node, and G and W are respectively a power generation node and a load node set.
Optionally, the calculation formula of the improved electrical permittivity value is:
wherein, Be(m, n) is the improved electrical permittivity; i isij(m, n) is the unit current element added between the power generation-load node pair (i, j), and the current variation of the line (m, n) when the load node j increases the unit load; pmnmaxIs the maximum transmission power, W, of the line (m, n)isAs power weight of the generating node i, WjsIs the power weight of the load node j,
is the transmission power weight between the power generation node and the load node.
Compared with the prior art, the invention has the beneficial effects that:
1. the method identifies the grid key line of the multipoint access photovoltaic power supply, accords with the energy development direction of new energy grid connection at the present stage, and accords with the requirement of the future intelligent grid safety development.
2. The invention introduces the maximum transmission power of the line, and improves the identification precision; meanwhile, the method comprehensively considers the topological structure, the power generation capacity, the load capacity and the distribution characteristics of the power grid, and can more truly and effectively evaluate the vulnerability of the power grid.
3. According to the invention, researches show that the change condition of the key circuit of the system under the condition of different photovoltaic power supply permeability is improved day by day, and the method has a certain guiding significance for avoiding the power grid blackout accident.
Drawings
In order that the present invention may be more readily and clearly understood, reference is now made to the following detailed description of the invention taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a wiring diagram of an IEEE-39 node system.
FIG. 3 is a diagram showing the result of line electrical medium number of the multi-photovoltaic power supply grid-connected at the power generation node.
Fig. 4 is a diagram showing the result of line electrical medium of multi-photovoltaic power supply grid-connected at load nodes.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
As shown in fig. 1, the present invention provides a method for identifying a critical line of a power grid of a multi-point access photovoltaic power supply, including:
(1) acquiring a direct current power flow network model of a power grid;
(2) traversing all 'power generation-load' pairs in the direct current power flow network model, injecting unit current elements into power generation nodes in all the 'power generation-load' pairs, injecting unit loads into load nodes, and recording current variation generated by all lines of a power grid when each node pair injects the unit current elements and the unit loads;
(3) traversing all 'power generation-load' pairs in the direct current power flow network model, judging whether photovoltaic power supply access exists in power generation nodes and load nodes in each 'power generation-load', updating power weights of the power generation nodes and/or the load nodes according to a judgment result, and then calculating transmission power weights between the power generation nodes and the load nodes;
(4) calculating an improved electrical dielectric value of each line based on the data obtained in the steps (2) and (3);
(5) and sequencing the improved electric medium values of all the lines to finish the identification of the power grid key lines of the multipoint access photovoltaic power supply.
In a specific embodiment of the present invention, the dc power flow network model is obtained based on a complex network theory. The direct current power flow network model is a undirected weighted graph G (V, E, Z, P, B), wherein the point set V comprises a generator, a contact node and a load node of a power grid; the side set E comprises a transformer branch of a power grid and a power transmission line; the side weight set Z comprises reactance values of the power transmission line; the transmission value set P comprises the maximum transmission power of the transmission line; the adjacency matrix B represents the structural relationship representing the power grid.
In a specific embodiment of the present invention, if it is determined that a certain power generation node is connected to a photovoltaic power supply, the power weight of the power generation node is calculated according to the following formula:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; sGThe node power injection increment generated by connecting a photovoltaic power supply to a power generation node; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of load node j.
If a certain load node is judged to be connected to the photovoltaic power supply, then:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of the load node j; swThe node power injection increment generated when the photovoltaic power supply is connected to a load node, and G and W are respectively a power generation node and a load node set.
In an embodiment of the present invention, the improved electrical dielectric value is calculated by the following formula:
wherein, Be(m, n) is the improved electrical permittivity; i isij(m, n) is the unit current element added between the power generation-load node pair (i, j), and the current variation of the line (m, n) when the load node j increases the unit load; pmnmaxIs the maximum transmission power, W, of the line (m, n)isAs power weight of the generating node i, WjsIs the power weight of the load node j,
is the transmission power weight between the power generation node and the load node.
The method for identifying the power grid key line of the multi-point access photovoltaic power supply provided by the invention is described in detail below by taking the IEEE-39 node system in fig. 2 as an example, and the identification effectiveness of the method is verified. The method comprises the following specific steps:
step 1: according to an IEEE-39 node system, simulating the identification of a power grid key line of a power generation node multipoint access photovoltaic power supply;
the IEEE-39 node system comprises 46 lines, 10 generator nodes and 19 load nodes, and the node 31 is selected as a balance node of the system.
According to the photovoltaic power supply system, a plurality of photovoltaic power supplies are respectively connected to the nodes 39, 30, 37, 35 and 32, the output of the photovoltaic power supplies is set to be 200MW, and the output fluctuation of the photovoltaic power supplies is set to be stabilized by the energy storage system. According to the identification method of the present invention, the line ranked as top 20 is shown in table 1, and the improved electrical medium result of the obtained line is shown in fig. 3.
TABLE 1
From table 1, it can be seen that, in addition to the medium-long range transmission line in the system, the line connecting multiple nodes, that is, the line connecting the heavy-load nodes, the lines near the outlet of the photovoltaic power supply are also the top-ranked lines, such as lines 21-22, lines 13-14, lines 1-2, lines 1-39 and lines 6-11, and the failure of these lines will result in the output power of part of the photovoltaic power supply or generator being insufficient to supply the local network power of the system. And the lines 16-17, 16-29 and the like which are ranked at the top belong to medium-long distance transmission lines in the system topology structure, and are connected with more nodes, and the power transmission of the generators 33, 34, 35 and 36 is caused to be in problem due to the faults of the lines, so that the power supply of local areas of the system is short. The identification method provided by the invention can reflect the network topology structure of the power grid, and can also reflect the influence of a plurality of photovoltaic power supplies after being connected to the grid on the system.
Step 2: according to an IEEE-39 node system, simulating the identification of a system key line of a load node multipoint access photovoltaic power supply;
according to the photovoltaic power supply system, a plurality of photovoltaic power supplies are respectively connected to the nodes 4, 3, 25, 29 and 16, the output of the photovoltaic power supplies is set to be 200MW, and the output fluctuation of the photovoltaic power supplies is set to be stabilized by the energy storage system. According to the identification method of the present invention, the line ranked as top 20 is shown in table 2, and the improved electrical medium result of the obtained line is shown in fig. 4.
TABLE 2
From table 2, it can be found that the photovoltaic power access load node has a greater influence relative to the photovoltaic power access power generation node. The lines at the top have small sequence change, but the electric medium values of the lines are changed, and the electric medium values of the photovoltaic power supply outlet lines such as 3-4, 3-18, 25-26, 16-17 and 16-24 are obviously changed.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and their equivalents.
Claims (6)
1. A power grid key line identification method of a multi-point access photovoltaic power supply is characterized by comprising the following steps:
(1) acquiring a direct current power flow network model of a power grid;
(2) traversing all 'power generation-load' pairs in the direct current power flow network model, injecting unit current elements into power generation nodes in each 'power generation-load' pair, injecting unit loads into load nodes, and recording current variation generated by all lines of the power grid when the unit current elements and the unit loads are injected into each node pair;
(3) traversing all 'power generation-load' pairs in the direct current power flow network model, judging whether photovoltaic power supply access exists in power generation nodes and load nodes in each 'power generation-load', updating power weights of the power generation nodes and/or the load nodes according to a judgment result, and then calculating transmission power weights between the power generation nodes and the load nodes;
(4) calculating an improved electrical dielectric value of each line based on the data obtained in the steps (2) and (3);
(5) and sequencing the improved electric medium values of all the lines to finish the identification of the power grid key lines of the multipoint access photovoltaic power supply.
2. The method for identifying the power grid key line of the multi-point access photovoltaic power supply as claimed in claim 1, wherein: the direct current power flow network model is a undirected weighted graph G (V, E, Z, P, B), wherein the point set V comprises a generator, a contact node and a load node of a power grid; the side set E comprises a transformer branch of a power grid and a power transmission line; the side weight set Z comprises reactance values of the power transmission line; the transmission value set P comprises the maximum transmission power of the transmission line; the adjacency matrix B represents the structural relationship representing the power grid.
3. The method for identifying the power grid key line of the multi-point access photovoltaic power supply as claimed in claim 2, wherein: the direct current power flow network model is obtained based on a complex network theory.
4. The method for identifying the power grid key line of the multi-point access photovoltaic power supply as claimed in claim 1, wherein: if the photovoltaic power supply is judged to be connected to a certain power generation node, calculating the power weight of the power generation node according to the following formula:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; sGThe node power injection increment generated by connecting a photovoltaic power supply to a power generation node; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of load node j.
5. The method for identifying the power grid key line of the multi-point access photovoltaic power supply as claimed in claim 4, wherein: if a certain load node is judged to be connected to the photovoltaic power supply, then:
wherein, WisIs the power weight of the power generation node i; wiTaking the rated capacity of the generator as the weight of the power generation node i; wjTaking the actual load as the weight of the load node j; wjsIs the power weight of the load node j; swThe node power injection increment generated when the photovoltaic power supply is connected to a load node, and G and W are respectively a power generation node and a load node set.
6. The method for identifying the power grid key line of the multi-point access photovoltaic power supply as claimed in claim 5, wherein: the calculation formula of the improved dielectric value is as follows:
wherein, Be(m, n) is the improved electrical permittivity; i isij(m, n) is the unit current element added between the power generation-load node pair (i, j), and the current variation of the line (m, n) when the load node j increases the unit load; pmnmaxIs the maximum transmission power, W, of the line (m, n)isAs power weight of the generating node i, WjsIs the power weight of the load node j,
is the transmission power weight between the power generation node and the load node.
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